Supplement Dangers

Receive the latest health updates in your inbox

Even though you can pick up dietary supplements like ginseng and St. John's Wort at a natural foods store without a prescription, that doesn't mean they're harmless. It doesn't necessary mean they are harmful, either. But despite estimates that one-third of adult Americans are taking dietary supplements, few studies have been done to demonstrate their benefits or side effects, leaving researchers and consumers unsure of their safety, especially when taken along with prescription and over-the-counter medications.

Under the Dietary Supplement Health and Education Act (DSHEA) of 1994, a dietary supplement includes vitamins, herbs or other botanicals, amino acids, dietary substances such as enzymes, and food extracts, such as the isoflavones in soybeans. Unlike prescription and over-the-counter medications, which must undergo rigorous scientific study before receiving Food and Drug Administration (FDA) approval, under DSHEA, the manufacturer is solely responsible for the safety of their product and the claims they make when marketing it. While the FDA requires manufacturers list ingredients on the product label, the quality of those ingredients does not have to be evaluated, nor does the amount of a given ingredient have to be listed. Even if the amount is listed, the products are not tested to ensure that amounts given on the label are accurate.

"The important thing is that herbal medications, which are in the category of the dietary supplements, are not as vigorously regulated by the FDA as prescription drugs," explains Chun-Su Yuan, MD, a professor in the department of anesthesia and critical care and the director of the Tang Center for Herbal Medicine Research at the University of Chicago. "So the FDA does not regulate them until the adverse effects actually happen. At that point, the FDA would step in, such as when ephedra-containing dietary supplements were banned at the end of last year."

Because of a report that ginseng had interacted with warfarin in a patient, Dr. Yuan and his colleagues conducted a study published in the July 6th issue of The Annals of Internal Medicine, examining whether the popular herbal supplement ginseng changes the effectiveness of warfarin, a drug given to people with certain cardiovascular conditions to prevent blot clots. The researchers evaluated American ginseng, which is a type of ginseng commonly taken for fatigue, immune function and general health. While ginseng may promote bleeding in surgical patients, it reduced the anti-clotting effect of warfarin in this study.

In the four-week study, researchers gave warfarin to two groups of healthy patients who did not have any condition requiring warfarin. Beginning the second week, they then gave one group of participants ginseng and one group a placebo. At the fourth week, the researchers took blood samples and found that the participants taking ginseng had lower blood levels of warfarin than those who took the placebo; there was also less of an effect on blood clotting in the ginseng group. The researchers concluded that ginseng should not be taken while patients are on warfarin. When prescribing warfarin, doctors should ask patients if they are taking ginseng and patients taking this herb should share that information with their doctor.

Below, Dr. Yuan discusses his study and the safe ways to approach the use of dietary supplements.

Why did you decide to conduct this study? Ginseng, like all other herbs, consists of a number of pharmacologically active ingredients that could have both beneficial effects and potential side effects or interactions with other drugs. There was a widely cited case report on a potential ginseng/warfarin interaction several years ago. However, there are few well-designed, controlled studies in humans in this area, so we decided to do the study on ginseng/warfarin interaction.

How does ginseng interact with warfarin? Warfarin is a commonly used drug that decreases the clotting activity of the blood by thinning it in order to prevent the development of clots or to prevent existing clots from getting bigger. Warfarin has a very narrow therapeutic index. In other words, the effective dose that is safe and the dose that may cause adverse events are very close. So if you are above the effective dose or below the effective dose, it may cause different pharmacologic activities. Tests for blood coagulation, or clotting, levels are done frequently in patients on wafarin to ensure the dose is appropriate. Other drugs and supplements may change the concentration of the warfarin in the blood, leading to clinical consequences. For example, the blood thinning effect may not be achieved, or someone may have bleeding because the blood won't clot.

After people in our study took ginseng for two weeks, we found that they had a lower blood level of warfarin, and that warfarin had less of an effect on blood clotting than it did it people who took the placebo.

Who might be at higher risk for adverse effects or interactions? Studies show, in general, that the incidence of adverse effects of herbs is much lower than that in prescription medications. So dietary supplements are fairly safe. But people who have medical conditions, as well as elderly people, pregnant women, and children, should be careful with dietary supplements.

Why should people tell their healthcare providers when they're taking supplements? Many consumers do not believe herbal medicines have pharmacologically active ingredients in them. So patients may not inform healthcare professionals, including their pharmacists, that they are taking herbal medicine. But supplements actually act like drugs, although they're not regulated like drugs. It is very important to educate consumers that herbs and other supplements may have adverse effects and herb/drug interactions, and that they need to provide their healthcare professionals with information about supplements.

It is also very important for the medical community to have adequate knowledge of dietary supplements. Many doctors like to stay away from herbal medicine. But the fact is about one-third, and some studies show that up to 50 percent of the US adult population is taking dietary supplements. So physicians and healthcare professionals should know enough about a supplement to be able to tell if there could be adverse effects or herbal/drug interactions.

In fact, the physician should ask the patient if they are taking particular herbs when prescribing medications that are known to interact with common herbs. For example, St. John's Wort, which is often taken as an antidepressant, can make the liver metabolize some drugs differently and reduce their effectiveness. In Europe, some young women taking oral contraceptives and St. John's Wort got pregnant because the herb reduced the birth control pill's concentration in the blood.

Some herbs and other dietary supplements have been shown to have beneficial effects, which also is important for a physician to know. For example, St. John's Wort may be effective in mild and moderate depression, and ginseng may help combat fatigue and improve immune function.

Should people keep a record of what supplements they are taking? We suggest that the patients should take all the bottles of the supplements they are taking to the doctor's office, especially, for example, before surgery. Some consumers don't really know what they are taking. And some may not follow the instructions on the label and take more or less than the recommended amount.

How can someone investigate supplements? Some manufacturers say their supplements are standardized, but those claims could be misleading in many cases. The US Pharmacopeia, a non-governmental organization, measures and analyzes some herbal compounds. Supplements that have been measured by the USP have a USP certification mark on their label. However, the USP can only measure certain ingredients, and a single herbal supplement can consist of many active ingredients. Another complicating factor is that all the cultivation conditions—the soil, the temperature, the moisture and even the length of the cultivation season—will make the ingredients in herbal supplements different.

However, there are several Web sites, including those of the FDA and the National Center for Complementary and Alternative Medicine, which is an organization in the National Institutes of Health, that have good information about the benefits and adverse effects of dietary supplements, including herb/drug interactions.